You get an even split of force/health with helps you have larger force pool before you change. Sentinels gain immunity to stun, fear and paralysis (pretty much anything nasty).
Starting as a sentinel will get you a good core of skills before you evolve in to the weaponmaster. Demolitions also becomes a class skill when you cross over, so you can save taking a feat there if you wait until then to put any more points in, if you wanted to. Then when you have those four at 30, you can start taking other skills just because. This will allow you to always keep Persuade, Computer Use, Security, and Repair maxed out, even when you become a Weapon Master.
KOTOR 2 JEDI WEAPON MASTER VS SITH MARAUDER FOR FREE
The only reason you take a point in it is so that you can use the ability to plant and recover mines, and the only reason you want to do that is for pre-Bao-Dur recovering mines for free XP, as well as a couple of pre-Bao-Dur loot containers that can only be opened with mines. I would stop Awareness and Treat Injury at 15, never put any points into Stealth, and rely on +Demolitions equipment to get additional points there. This will allow your main character to be almost self-sufficient in skills. Start with 16 INT, save four skill points at first level, take Class Skill: Repair feat at first level, and take one (cross-class) point in Demolitions at second level. I think that's better anyway, personally. You lose Force Jump, but you gain Force Immunity. You have slightly less health (-2 per level) and one less feat, but so much more skills.